The approaches adopted so far in China to calculate reserves of ore deposits have largely been dependent on polygonal methods, including a cross-section method and a geological block method. However, for various reasons, especially, the complexity of the geology, and the ore bodies, the deposits became gradually known as development and exploitation took place. There is a certain difference between the geological and cutoff grade at the stage of geological prospecting and mining, which will have a great impact on both mine construction and production. As much accurate information as possible on the spatial distribution patterns of ore bodies and global reserves is essential to improve the production efficiency and reduce production cost. The 10-9 ore body of Lutangba in the Gejiu Tin Deposits was selected as our research object, using a log Kriging and an inverse distance weighing method. In our paper the results are compared with the reserves calculated by the polygonal block method. The global estimate and estimation errors associated with each estimation method are discussed.